Downregulation of Ras gap expression in K562 cells correlates with increased differentiation to macrophages but does not affect cell proliferation or survival.

We have studied the role of Ras GTPase activating protein (GAP) in the chronic myeloid leukaemia cell line K562 by downregulating its expression using antisense RNA. This had no effect on cell proliferation and survival, suggesting that other effector molecules mediate these roles of Ras. Differentiation to macrophages following treatment with the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate was found to correlate with a significant increase in expression of GAP in K562 cells. When GAP expression was downregulated by antisense RNA, the degree of macrophage differentiation was increased, implicating GAP in the regulation of macrophage differentiation.